1. Field of the Invention
The present invention relates to a treating method of a workpiece and, more particularly, to temperature control in deposition of a metal on a surface of a semiconductor substrate.
2. Description of the Related Art
In a conventional manufacturing process of semiconductor integrated circuits, physical vapor deposition (PVD), such as evaporation and sputtering deposition, is used as a technique for depositing a metal on a surface of a substrate. However, with advances in integration, speed, and density of an integrated circuit as in an ultra large scaled integrated circuit (ultra LSI), a great deal of attention has been paid to a technique for depositing a refractory metal, e.g., W (tungsten), having a resistance which is 1/10 or less that of polycrystalline silicon, in order to form a gate electrode and perform selective deposition of a metal in contact holes and through holes.
For such a purpose, chemical vapor deposition, which is excellent in deposition selectivity, is widely utilized. When a W thin film is to be selectively deposited on a substrate, e.g., a substrate having an aluminum film formed on its surface, by chemical vapor deposition, the substrate must be quickly heated, and its temperature must be controlled to a desired temperature afterward in order to improve deposition selectivity. In this case, the temperature of the substrate must be accurately detected for its temperature control. The following two methods are available for detection of the temperature: a method of detecting the temperature of a substrate by bringing a thermocouple as a contact type temperature detecting device into contact with the substrate; and a method of detecting the temperature of a substrate by detecting the radiation energy of infrared rays from the substrate using a pyrometer as a non-contact type temperature detecting device.
If, however, a thermocouple is used for temperature detection in order to perform such temperature control of a substrate, high reliability can be expected with respect to stable temperatures, but reliability is decreased with respect to quickly rising temperatures because it takes a considerably long period of time to increase the temperature of the thermocouple itself. Therefore, when the substrate is quickly heated, the thermocouple cannot follow the temperature rise. As a result, the difference between a temperature detected by the thermocouple and an actual temperature becomes large, and a set value to be kept constant after quick rise is greatly overshot. If such overshoot occurs, when a surface of the substrate consists of aluminum, the surface is melted. Hence, a CVD process cannot be performed. In addition, if CVD is to be applied onto a diffusion region of a silicon substrate, the reaction advances into the substrate, i.e., a phenomenon called "encroachment" occurs.
In contrast to this, if a pyrometer is used for temperature control of a substrate, the pyrometer can properly respond to quick heating because it has good response characteristics. However, when deposition of a metal on a surface of the substrate is started, since the emissivity of infrared rays radiated from the surface of the substrate prior to deposition is different from that of a deposited film material, emissivity of infrared rays radiated from the surface of the substrate is changed as deposition progresses. The pyrometer cannot follow this change. Therefore, temperature detection cannot be properly performed.